media: mx_emmaprp: Implement wait_prepare and wait_finish

This driver is currently specifying a video_device lock,
which means it is protecting all the ioctls (including
queue ioctls) with a single mutex.

It's therefore straightforward to implement wait_prepare
and wait_finish, by explicitly setting the vb2_queue lock.

Having these callbacks releases the queue lock while blocking,
which improves latency by allowing for example streamoff
or qbuf operations while waiting in dqbuf.
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/platform/mx2_emmaprp.c

@@ -733,6 +733,8 @@ static const struct vb2_ops emmaprp_qops = {
 	.queue_setup	 = emmaprp_queue_setup,
 	.buf_prepare	 = emmaprp_buf_prepare,
 	.buf_queue	 = emmaprp_buf_queue,
+	.wait_prepare	 = vb2_ops_wait_prepare,
+	.wait_finish	 = vb2_ops_wait_finish,
 };
 
 static int queue_init(void *priv, struct vb2_queue *src_vq,
@@ -749,6 +751,7 @@ static int queue_init(void *priv, struct vb2_queue *src_vq,
 	src_vq->mem_ops = &vb2_dma_contig_memops;
 	src_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
 	src_vq->dev = ctx->dev->v4l2_dev.dev;
+	src_vq->lock = &ctx->dev->dev_mutex;
 
 	ret = vb2_queue_init(src_vq);
 	if (ret)
@@ -762,6 +765,7 @@ static int queue_init(void *priv, struct vb2_queue *src_vq,
 	dst_vq->mem_ops = &vb2_dma_contig_memops;
 	dst_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
 	dst_vq->dev = ctx->dev->v4l2_dev.dev;
+	dst_vq->lock = &ctx->dev->dev_mutex;
 
 	return vb2_queue_init(dst_vq);
 }